Up-flow headbox



June 25, 1963 P. H. GoLDsMl-TH 3,095,348

UP-FLow HEADBOX Filed March 51, 1960 2 Sheets-Sheet 1 Pff/UP h. SunSun/f70 ww/f PUMP NEW STOCK FRU 1g SCREEN June 2,5, 1963 P. H. GoLDsMl-T-HuP-FLow HEADBOX 2 Sheets-Sheet 2 Filed March 3l, 1960 Ilm= *Ill

ENZ-"wm United States Patent Omce 3,095,348 Patented June 25, 19633,095,348 UP-FLOW HEADBOX Philip H. Goldsmith, 4300 Western Ave., Apt.512, Montreal, Quebec, Canada Filed Mar. 31, 1960, Ser. No. 19,076 8Claims. (Cl. 162--216) The invention relates to the art of papermakingand more particularly to an up-flow type of headbox for use inconjunction with a papermaking machine.

In most papermaking machines the sheet or web is formed by bringing apaper stock comprising 4a pulp suspension into contact with a-foraminous forming surface and permitting or causing the water of thepulp suspension to flow through the holes in the forming surface leaving`a matted layer of fiber on the forming surface. The paper stock isusually supplied under a hydraulic head sufficient to cause a desiredflow of stock to the forming surface and it has been common practice toobtain this head by employing an open top rectangular box, commonlycalled a headbox, in which a level of stock is maintained at asufficient height yabove the forming surface to give 4the desired head.

As is well known, a paper stock `is Ifrequently composed of variouscomponents including water which has drained through the forming surface(commonly called white water), recirculated stock, and fresh incomingstock. It has yalso been common practice to mix the various componentsof the paper stock in the headbox. According to this practice each ofthe components is introduced into the headbox through a separate pipeand it has been assumed that the natural turbulence resulting from sucha procedure would produce adequate mixing. However, this is not usuallyaccomplished under present day operating conditions. Pockets ofdifferent consistency stocks tend to form in the corners of the headboxand this segregation causes streaks of uneven consistencies of stock topass to the forming surface and cause irregularities in the sheet.Thesel irregularities tend to produce blemishes in the formation,irregular caliber in finish across the sheet, and numerous operatingtroubles. It is also desira- -ble that air or other gaseous materials beremoved from the mixed `stock before it passes to the forming surface.It has been assumed that adequate elimination of air could be obtainedwith the conventional type of headbox referred -to above, whereasactually the extreme turbulence of the mixing operation in a normalheadbox tends to increase the air content of the stock.

In a prior patent of the applicant, namely U.S. Patent 2,393,244, whichissued January 22, 1946, one way of overcoming this problem was Solvedby providing -an up-flow headbox comprising an outer inverted cone andan inner inverted cone concentric therewith and forming an annular spacetherebetween. The term upflow may be one that is not generally known inthe prior art and is descriptive of the flow arrangement shown in U.S.Patent 2,393,244. For the purpose of the present description it will beunderstood that upflow headbox refers to a headbox having a flowarrangement of this type.

In the construction of U.S. Patent 2,393,244 stock was delivered so asto ilow upwardly through the inner cone at a constantly decreasingvelocity passing over a dam formed by the upper edge of the inner coneso that it flowed downwardly through the annular space between the twocones at a constantly increasing rate. Because of the upper direction ofthe flow of the incoming stock in the relatively llow stock velocity atthe overflow dam this form of headbox is well adapted to remove air vandother gaseous materials from the stock and improve the r smoothness offlow. However, in order to achieve the desired mixing step, this wasundertaken `by the provision of mixing devices incorporated in conduitlines leading from the papermaking machine. In other words, the mixingstep and the air removal step were physically separated one from theother so that the mixing was accomplished before the stock reached theheadbox and therefore did not interfere With the desired functions whichare the maintenance of a constant iow level and the elimination of airor other gaseous material from the stock.

The present invention aims to provide an improvement on the conicalup-flow type of headbox disclosed in U.S. Patent 2,393,244 by providinga means of directly mixing the various components of stock in theheadboX, thus eliminating the necessity of the remote mixing devices,and at the same time eliminating the disadvantages of the commonly usedtype of headboxes with respect to the elimination of air or othergaseous materials.

The advantages of the headbox of the present invention may be bestappreciated by reference to the accompanying drawings which illustrate apreferred form of the headbox incorporated in a paper machine of thecylinder type and in which:

FIGURE l is a diagrammatic View of an up-flow headbox-mixer constructionin accordance with the present invention as combined with a papermachine of the cylinder type.

FIGURE 2 is a View corresponding to FIGURE 1 with the headbox, cylindermold, vat, and ilow spreader shown in section to illustrate theconstruction more clearly.

FIGURE 3 is a view of the upper portion of the headbox-mixer of FIGURE 1along the line 3--3 to show the tangential placing of the vacuum conduitleading from the cylinder mold.

FIGURE 4 is a cross-sectional view of the lower portion of theheadbox-mixer construction of FIGURE l along the line 4 4.

Referring to the drawings, and more particularly to FIGURE l, there isshown a vat of generally rectangular shape indicated at 10 andcontaining a foraminous cylinder mold 12 rotatably supported by thebearings 13, only one of which is shown. The particular Vat and cylindermold shown is of the adjustable cylinder type as shown in the applicantsU.S. Patent 2,658,428, November l0, 1953. The mechanism for rotating thecylinder mold 10 and the internal construction in general forms no partof the present invention and therefore is not shown in detail.

Stock is supplied to the vat 10 through a flow spreader 14 which is ofsuch shape and cross-sectional area as to spread the flow of stock tothe full machine width with substantially no change or with an increasein s tock Velocity. The type of flow spreader shown is that illustratedand described in the applicants copending application Serial No.856,457, filed December 1, 1959.

Upon entering the vat 10` the stock passes through a conduit 38 (seeFIGURE 2) to the outer vat circle space 40 which is formed by an outerVat circle 42 of generally cylindrical contour and an inner adjustablevat circle 44. The outer vat circle 42 is `secured to the vat ends andthe vat circle 44 is adjustable -by suitable means, for example as shownin the applicants U.S. Patent 2,658,428, as previously mentioned. Fromthe vat circle space 40 the stock flows over the smoothly curved upper.end 411 of Vat circle 44 into the inner vat circle 43. The curvedsurface 41 is analogous to the known making boards and may be sodescribed.

As the stockpasses through the inner vat circle space 43 the cylindermold 12 rotates in a counter-clockwise direction, as shown, and aportion of the water passes w,through the forarninous surface of thecylinder mold forming a web of fibers on the surface of the mold whichis removed from the top of the mold after it has emerged from the stock.The water passing through the mold, known in the art as white water, isremoved in a manner as will be described later. In the preferredconstruction illustrated, a vacuum pipe 34 connected to the interior ofthe mold 12 aids in the extraction of the Iwater and picks up any whitewater which may be carried upward by the mold. The circulating excessstock from the vat circle space 43 passes over an adjustable dam (notillustrated) and over the back end 45 of the inner vat circle 44 andleaves the vat through a conduit or pipe 47 to be recirculated in amanner hereinafter described.

The water which flows through the surface of the cylinder mold 12 isremoved at the ends of the mold and ows into a white water compartment51 at the ends of the vat. The white Water compartment 51 is providedwith adjustable dams (not illustrated) so that the portion of the Whitewater that overflows these dams is the excess White water which ows fromthe white water compartment through a pipe 53 to a suitable point ofdisposal. The remainder of the white water, constituting the majorportion thereof, is carried from the white water compartment through thepipe 55 where it is again divided, one portion flowing through the pipe56 where it is mixed with new stock fed through a pipe 58 as a diluentwith the new stock and white Water passing to a pump 61, and then by thepipe 59 to the screen or screens (not shown).

Again with reference to FIGURE 1 and 2, the upllow headbox-mixerconstruction of the invention cornprises an outer inverted cone 22 andan inner inverted cone 20 concentric therewith and forming an annularspace 23 therebetween. The bottom portion of the outer cone 22 is closedand stock delivered to the annular space 23 therebetween, as Will bedescribed in more detail later, proceeds about the annular space untilit reaches the top of the inner cone 20 and out of the headbox to theflow spreader 14.

This mixer-headbox construction of inner and outer cones, in onepreferred arrangement shown, is provided with a cover 30 to which lavacuum pipe 32 is connected and the vacuum pipe 34, as previouslymentioned, extends from the suction connection of the cylinder mold tothe upper portion of the headbox and enters the same tangentially sothat any white water picked up by the vacuum line 34 will be dischargedwith the white water entering the up-flow headbox from the white waterdelivery pipe 55, as will be described in more detail later.

As shown most clearly in FIGURES l and 2, the new stock is delivered tothe outer cone 22 through a conduit 60 leading from the screen orscreens (not illustrated) and the white water is delivered to the outercone 22 through the pipe 55. The circulating excess stock is alsodelivered to the outer cone 22 through the conduit 47. As shown inFIGURE 4, the white water and circulating stock are preferablyintroduced tangentially into the outer cone 22 so as to impart acircumferential motion to the stock being delivered thereto, therebylengthening its travel and increasing its time within the headbox whichfurther aids in air or gas escape. The new stock delivered from theconduit 60, in the preferred construction shown, enters the outer cone22 substantially directly across the circumferential flow so as toimpinge against the inner cone 20 and create la further turbulenceaiding in the desired mixing action. The mixture of new stock, whitewater, and circulating stock as it passes upwards in a circumferentialow and at a decreasing velocity through the tapering annular spacebetween the inner and outer cones is intimately mixed in this initialtravel and again mixed and blended as they proceed downwards through theinterior of the inner cone 20 at a gradually increasing velocity.

The mixed and deaerated stock passes from the inner cone 20 through apipe 61 to the suction side of a vat pump and from the vat pump 65 isdelivered to the first pass of the ow spreader 14 through a pipe 67.

In the preferred construction shown the provision of the vacuum pipe 32and the covering of the headbox acts to further eliminate any air orother gaseous material. Since the vacuum within the headbox is the sameas that within the cylinder rnold (common source) the level of stockWithin the headbox remains substantially the same as that Within thecylinder mold regardless of the degree of vacuum applied. This ispossible due to the headbox being on the suction side of the pump. Thestock as delivered through the pipe 59 by the pump 65 to the flowspreader 14 has been intimately mixed and deaerated providing thenecessary characteristics for a smooth and uniform flow through the flowspreader into the interior of the cylinder machine.

A further feature of the present construction arlsing out of thepreferred vacuum arrangement described is that it provides a waterseparator for suction lines of cylinder molds. As previously described,there is a tendency for water within the interior of the cylinder moldto be picked up during its rotation and this is intensied when themachine is operated at higher speeds. As the present vacuum connectionfrom the mold to headbox picks up this water and returns to the system,in a tangential manner so that it does not splash down and entrain air,there is no loss of Water except the normal run olf of the excess,insuring stability of operation. This is particularly applicable to acylinder mold permitting vacuums on the order of several inches ofmercury vacuum (about from 1 to 5 inches mercury or more) as is possiblein the type of cylinder mold shown in applicants U.S. Patent 2,509,296,issued May 30, 1950.

As can be seen most clearly in FIGURES l and 2, the flow systemillustrated is a gravity feed with the circulation being from screensand cylinder vat to the outer cone 22, mixed and deaerated within theannular space 23 and out of the inner cone 20 to the suction side of thevat pump 65 where the flow is given sufficient pressure to pass throughthe flow spreader 14 into the cylinder vat 10. The height of the top ofthe inner cone 20 is maintained substantially level with the bottom ofthe cylinder mold 12. By this arrangement the stock is initially mixedat the lowest point of the headbox where the velocities are greatest andis furthest from the free surface to avoid air entrainment. Further, asthe stock flows up towards this free surface the speed of ow isdecreased permitting the air to work through as the circulating flowdecreases in velocity till at its slowest point at the air surface itprogresses down through the center of the inner cone 20 and the flowincreases in speed as it progresses down to the suction side of thepump. To avoid any accumulation of residual air the pipe 67 leading fromthe vat pump 65 is sloped upwardly and a vent pipe 69 leads from the topof this run directly into the white water pipe 55. A similar vent pipe70 leads from the top of the rst turn-around of the ow spreader 14, alsoto the pipe 55. The white water pipe 55 is also inclined upwardlytowards its connection with the outer cone 22 so that any air travelsupwardly into the outer cone 22 and is discharged during the upwardmovement of the stock.

While the preceding description and accompanying drawings refer to apreferred construction adapted for use in connection with a suction typecylinder machine, it will be appreciated that the up-flow mixer-headboxconstruction of the invention is suitable for use in cornbination withother standard types of cylinder machines. lf it is used with a standardcylinder mold arrangement without vacuum the cover 30 and vacuum pipes32, 34 would not be necessary.

I claim:

1. In a paper machine of the type wherein a sheet is formed by bringinga paper stock into contact with a forming surface, a combinedheadbox-mixer comprising: a vertically arranged outer conduit having acrosssec r tional area that increases gradually and continuously fromthe bottom of said outer conduit to adjacent the top of said outerconduit, an inner conduit vertically arranged Within said outer conduitand having a cross-sectional area that increases gradually from thebottom of said inner conduit to the top of said inner conduit; saidinner and outer conduits being coaxially arranged with the taperingannular space therebetween constituting a mixing chamber, the upper edgeof said inner conduit serving as an overow means, means for supplyingstock to the said mixing chamber between said inner and outer conduitsat a point near the bottom of said outer conduit, and means forwithdrawing stock from said inner conduit at a point near the bottom ofsaid inner conduit, whereby stock delivered to said outer conduit owsupwardly in a spiral path through said mixing chamber at a graduallydecreasing velocity, over said overflow means into the inner conduit andall the stock passing over said overilow means flows downwardly throughsaid inner conduit at a gradually increasing velocity.

l2. A machine as claimed in claim l, wherein at least part of said stockis delivered tangentially into the lower portion of said mixing chamber.

3. IIn a paper machine of the type wherein a sheet is formed by bringinga paper stock into contact with a forming surface, a combinedheadbox-mixer comprising: a vertically arranged outer conduit having across-sectional area that increases gradually and continuously from Ithebottom of said outer conduit to the top of said outer conduit, an innerconduit vertically arranged within said outer conduit and having across-sectional area that increases gradually from the bottom of saidinner conduit to the top of said inner conduit, said inner and outerconduits being coaxially arranged with the annular space therebetweenconstituting a mixing chamber, the upper edge of said inner conduitserving as an overflow means, the upper and lower ends of said outerconduit being sealed and a vacuum means connected into said outerconduit, means for supplying stock to the said mixing chamber betweensaid inner and outer conduits at a point near the bottom of said outerconduit, and means for withdrawing stock from said inner conduit at apoint near the bottom of said inner conduit, whereby stock delivered tosaid outer conduit ows in a spiral path upwardly through said mixingchamber at a gradually decreasing velocity, over said lover-flow meansinto the inner conduit and all the stock passing over said overow meansflows downwardly through said inner conduit at a gradually increasingvelocity.

4. A machine as claimed in claim 3, wherein at least part of said stockis delivered tangentially into the lower portion of said mixing chamber.

5. In a cylinder machine having a cylinder mold mount ed for rotationwithin a cylinder vat, :a system of combining, mixing, deaerating, anddelivery of dilute stock to said cylinder vat, including a headbox-mixerconstruction of combined inner and -outer casing of tapering conicalform, said headbox inner and outer casings being concenltrically spacedone Within the other with the upper larger end of said inner casingterminating below the upper larger end of said outer casing, -a whiteWater delivery conduit leading from said cylinder vat lto the lower endof said outer casing, a recirculating stock delivery conduit leadingfrom said cylinder vat to the lower end of said outer casing, a freshstock delivery conduit leading from a source of supply to the lower endof said outer casing, the inner terminal ends of said white water,recirculating stock, and fresh stock delivery conduits beingcircumferentially spaced within said outer casing lower end, said innercasing lower end having a discharge outlet, a dilute stock dischargeconduit leading from said inner casing discharge outlet, a pump havingits suction side connecte-d to said dilute stock discharge conduit, andla dilute stock ilow spreader connected to the discharge side of saidpump, said dow spreader leading into said cylinder vat, whereby separatestreams of white water, recirculating stock and fresh stock are combinedand caused to follow a spiral path upwards between said inner and outercasings at la gradually decreasing velocity up to the said upper end ofsaid casing and down through s-aid inner casing at a graduallyincreasing velocity to discharge as mixed, Iaerated, dilute stock, andby said pump delivered through said ilow spreader to said cylinder vat.

6. A system as claimed in claim 5, including a cover connected to saidouter casing, a conduit extending between said cover and cylinder mold,and a connection to said cover from a vacuum pressure source.

7. The method of forming a fibrous web from dilute stock on a cylindermold of a cylinder paper machine, comprising the steps of delivering thewhite water leaving the mold, fresh stock and recirculated stock inseparate streams to a common mixing zone having an entry point and adischarge point, combining said streams at said mixing zone entry pointand confining said combined streams within said mixing zone :to follow aspiral ow path raising at a gradually decreasing velocity to apredetermined point of maxium area within said zone and from said pointdescending at a gradually increasing velocity to said zone dischargepoint thereby simultaneously intimately mixing and deaerating saidcombined ilow of white Water, fresh and circulated stock, and from saidmixing zone discharge point delivering said mixed, deaerated, dilutedstock to the cylinder mold.

8. The method as claimed in claim 5, including the additional step ofapplying a vacuum to said mixing zone above said predetermined point Iofmaxium area.

References Cited in the le of this patent UNITED STATES PATENTS1,853,849 De Grew Apr. l2, 1932 2,393,244 Goldsmith Ian. 22, 19462,509,296 Goldsmith May 30, 1950 2,849,930 Freeman et al. Sept. 2, 19582,869,674 Vandenburgh Jan. 20, l959 2,876,860 Clark et al. Mar. 10, 1959

7. THE METHOD OF FORMING A FIBROUS WEB FROM DILUTE STOCK ON A CYLINDERMOLD OF A CYLINDER PAPER MACHINE, COMPRISING THE STEPS OF DELIVERING THEWHITE WATER LEAVING THE MOLD, FRESH STOCK AND RECIRCULATED STOCK INSEPARATE STREAMS TO A COMMON MIXING ZONE HAVING AN ENTRY POINT AND ADISCHARGE POINT, COMBINING SAID STREAMS AT SAID MIXING ZONE ENTRY POINTAND CONFINING SAID COMBINED STREAMS WITHIN SAID MIXING ZONE TO FOLLOW ASPIRAL FLOW PATH RAISING AT A GRADUALLY DECREASING VELOCITY TO APREDETERMINED POINT OF MAXIMUM AREA WITHIN SAID ZONE AND FROM SAID POINTDESCEDING AT A GRADUALLY INCREASING VELOCITY TO SAID ZONE DISCHARGEPOINT THEREBY SIMULTANEOUSLY INTIMATELY MIXING AND DEAERATING SAIDCOMBINED FLOW OF WHITE WATER, FRESH AND CIRCULATED STOCK, AND FROM SAIDMIXING ZONE DISCHARGE POINT DELIVERING SAID MIXED, DEAERATES, DILUTEDSTOCK TO THE CYLINDER MOLD.